Cell Membrane Transport Key terms

Selective Permeability

Passive Transport

Movement of substance across a membrane with no energy required Molecules from in response to a concentration gradient (ie. from high to low = down the gradient) 3 mechanisms: simple diffusion, facilitated diffusion, osmosis (water)

Diffusion

Moving across a concentration gradient from high to low. 3 mechanisms: simple diffusion, facilitated diffusion, osmosis (water)

Simple diffusion – no energy, no transport protein, move down concentration gradient, small, nonpolar hydrophobic

Facilitated diffusion

no energy, yes transport protein, down concentration gradient, small, polar, ion

Osmosis

Diffusion of water across a membrane, water moves from an area of high water concentration to one of low water concentration. No energy, yes transport protein, down water concentration gradient, water.

Tonicity (not from list but probably need to know)

describes how the extracellular solution can change the volume of a cell by affecting osmosis, often correlated with Osmlarity of a solution

Osmolarity (not from list but probably need to know)

describes the total solute concentration of solution (permeable and non permeable solutes) and is determined if a cell is hypertonic, isotonic, or hypotonic to its extracellular solution

Hypertonic extracellular fluid

lower osmolarity than the cytosol — water leaves the cell

Isotonic extracellular fluid

same osmolarity as the cytosol

Hypotonic extracellular fluid

higher osmolarity than the cytosol — water enters the cell (organisms who have cell walls ex plants, fungi, bacteria, prefer hypotonic extracellular solutions)

Turgor

The pressure exerted by the plasma membrane against the cell wall

Lysis

The breaking down or destruction of a cell membrane, which causes the cell to burst and release its inner contents

Plasmolysis

Hypertonic solutions cause this, as plant plasma membrane detaches from the cell wall

Facilitated transport

Active transport

Used anytime an ion or molecule is transported through a membrane protein Against its concentration gradient (low → high) Or Agaisnt its electrochemical gradient … Energy is always required, there is a transport protein too Two types: primary active transport and secondary active transport. (Additional: Bulk Transport)

Primary Active Transport

moves an ion or molecule up its concentration gradient using energy from ATP hydrolysis

Secondary Active Transport

uses an electrochemical gradient created by primary active transport to move a different substance against its concentration gradient

Bulk Transport

Sometimes cells need to import or export molecules/particles that are too large to pass through a transport protein, so Importing (endocytosis) and exporting (exocytosis) by bulk transport is used

exo/endocytosis

Exocytosis

exporting by bulk transport

Endocytosis

importing by bulk transport

3 Types of Endocytosis

Phagocytosis, pinocytosis, receptor mediated endocytosis

Phagocytosis (cellular eating)

The cell membrane surrounds a particle and engulfs it

Pinocytosis (cellular drinking)

The cell membrane invaginates, surrounds a small volume of fluid, and pinches it off

Receptor mediated endocytosis

Uptake of a specific substance is target by binding to receptors on the external surface of the membrane